A high power buck derived non-isolated AC/DC LED driver

Facing the problem of high-cost, low-efficiency and complicated control of existing isolated led drivers, a high power low cost non-isolated Buck converter with coupled winding and stacked output is proposed. The input current idle time decreases which occurs when the input voltage is lower than part of output voltage, comparing to the conventional Buck´s whole output voltage. Therefore, the Buck derived LED driver can achieve high PF and its current harmonics can meet the IEC61000-3-2 Class C limits. This paper analyzes the operating principle of the circuit and the design methodology and criteria for high efficiency and low harmonics of the proposed Buck converter are presented. A 150-W prototype designed according to the proposed design criteria shows that the input current harmonics meet the IEC61000-3-2 (Class C) standard and power factor (PF) is higher than 0.95. The total harmonic distortion (THD) of the proposed converter is less than 20%. And the peak efficiency is higher than 97.2%.